The present invention relates to a power transmitting system for a hybrid motor vehicle using an internal combustion engine and an electric motor.
Recently, there has been developed the hybrid vehicle which is driven by the engine and the motor from the point of view of low pollution and resource economy.
In the hybrid motor vehicle, two motors which are selectively used as a power source and as a power generator are mounted, thereby increasing energy efficiency and driving performance.
Japanese Patent Application Laid Open 9-46821 discloses a hybrid motor vehicle in which a power distribution mechanism using a differential distributor such as a differential gear is used for distributing a part of engine power for a power generator so that the power by power generator is used for driving a motor so as to drive the motor vehicle.
Japanese Patent Application Laid Open 9-100853 discloses a hybrid motor vehicle where a planetary gear is provided for distributing engine power to a power generator.
However, in the above described prior arts, a great part of the driving power at low vehicle speed is relied in the motor. Accordingly, it is necessary to mount a large motor having a large output, and to provide a power generator having a large power in order to maintain a constant running performance. As a result, the cost for manufacturing the motor vehicle increases.
Furthermore, in the case that the rotation speed of the output shaft of an engine changes over a control range for controlling the motor speed, it is difficult to properly control the engine and the motor in response to requested driving force, only by distributing the power of the engine to the power generator.